Plant signaling & behavior (Plant Signal Behav )

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  • ISSN
    1559-2324

Publications in this journal

  • Anja Thalhammer, Dirk K Hincha
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    ABSTRACT: Abstract Plants as sessile organisms are strongly challenged by environmental stresses. Many plants species are able to cold-acclimate, acquiring higher freezing tolerance upon exposure to low but non-freezing temperatures. Among a plethora of adaptational processes, this involves the accumulation of cold regulated (COR) proteins that are assumed to stabilize and protect cellular structures during freezing. However, their molecular functions are largely unknown. We recently reported a comprehensive study of two intrinsically disordered cold regulated chloroplast proteins, COR15A and COR15B from Arabidopsis thaliana. They are necessary for full cold acclimation. During freezing, they stabilize leaf cells through folding and binding to chloroplast membranes. Contrary to evidence from in-vitro experiments, they play no role in enzyme stabilization in vivo. Elucidating these major functional and structural characteristics and estimation of protein abundance allow us to propose a detailed model for the mode of action of the two COR15 proteins.
    Plant signaling & behavior 12/2014;
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    ABSTRACT: In the current work, we investigated the effects of dopamine, an neurotransmitter found in several plant species on antioxidant enzyme activities and ROS in soybean (Glycine max L. Merrill) roots. The effects of dopamine on SOD, CAT and POD activities, as well as H2O2, O2(•-), melanin contents and lipid peroxidation were evaluated. Three-day-old seedlings were cultivated in half-strength Hoagland nutrient solution (pH 6.0), without or with 0.1 to 1.0 mM dopamine, in a growth chamber (25°C, 12 h photoperiod, irradiance of 280 μmol m(-2) s(-1)) for 24 h. Significant increases in melanin content were observed. The levels of ROS and lipid peroxidation decreased at all concentrations of dopamine tested. The SOD activity increased significantly under the action of dopamine, while CAT activity was inhibited and POD activity was unaffected. The results suggest a close relationship between a possible antioxidant activity of dopamine and melanin and activation of SOD, reducing the levels of ROS and damage on membranes of soybean roots.
    Plant signaling & behavior 11/2014;
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    ABSTRACT: Little is known on the molecular bases of plant - fungal interactions in orchid mycorrhiza. We developed a model system to investigate gene expression in mycorrhizal protocorms of Serapias vomeracea colonised by Tulasnella calospora. Our recent results with a small panel of genes as indicators of plant response to mycorrhizal colonization indicate that genes related with plant defence were not significantly up-regulated in mycorrhizal tissues. Here, we used laser microdissection to investigate whether expression of some orchid genes was restricted to specific cell types. Results showed that SvNod1, a S. vomeracea nodulin-like protein containing a plastocyanin-like domain, is expressed only in protocorm cells containing intracellular fungal hyphae. In addition, we investigated a family of fungal zinc metallopeptidases (M36). This gene family has expanded in the T. calospora genome and RNA-Seq experiments indicate that some members of the M36 metallopeptidases family are differentially regulated in orchid mycorrhizal protocorms.
    Plant signaling & behavior 11/2014;
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    ABSTRACT: Abstract Growth is the best visible sign of plant comfort. If plants are under stress, a difference in growth with control conditions can indicate that something is going wrong (or better). Phytohormones such as auxin, cytokinins, brassinosteroids or giberellins, are important growth regulators and their role in plant growth was extensively studied. On the other hand the role of salicylic acid (SA), a phytohormone commonly connected with plant defence responses, in plant growth is under-rated. However, studies with SA-overaccumulating mutants directly showed an influence of SA on plant growth. Recently we characterized an Arabidopsis SA-overaccumulating mutant impaired in phosphatidylinositol-4-kinases (pi4kIIIβ1β2). This mutant is dwarf. The crossing with mutants impaired in SA signalling revealed that pi4kIIIβ1β2 stunted rosette is due to high SA, while the short root length is not. This brings into evidence that upper and lower parts of the plants, even though they may share common phenotypes, are differently regulated.
    Plant signaling & behavior 11/2014;
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    ABSTRACT: Abstract Plants face many different concurrent and consecutive abiotic and biotic stresses during their lifetime. Roots can be infected by numerous pathogens and parasitic organisms. Unlike foliar pathogens, root pathogens have not been explored enough to fully understand root-pathogen interactions and the underlying mechanism of defense and resistance. PR gene expression, structural responses, secondary metabolite and root exudate production, as well as the recruitment of plant defense-assisting "soldier" rhizosphere microbes all assist in root defense against pathogens and herbivores. With new high-throughput molecular tools becoming available and more affordable, now is the opportune time to take a deep look below the ground. In this addendum, we focus on soil-borne Fusarium oxysporum as a pathogen and the options plants have to defend themselves against these hard-to-control pathogens.
    Plant signaling & behavior 11/2014;
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    ABSTRACT: Transport of proteins containing a nuclear localization signal (NLS) into the nucleus is mediated by nuclear transport receptors called importins, typically dimmers of a cargo-binding α-subunit and a β-subunit that mediates translocation through the nuclear pore complexes (NPCs). However, how proteins without canonical NLS move into the nucleus is not well understood. Recent results indicate that phospholipids, such as phosphatidic acid, play important roles in the intracellular translocation of proteins between the nucleus and cytoplasm.
    Plant signaling & behavior 11/2014;
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    ABSTRACT: Abstract Stress has a negative impact on crop yield by altering a gain in biomass and affecting seed set. Recent reports suggest that exposure to stress also influences the response of the progeny. In this paper, we analyzed seed size, leaf size, bolting time and transposon expression in two consecutive generations of Arabidopsis thaliana plants exposed to moderate UV-C stress. Since previous reports suggested a potential role of Dicer-like (DCL) proteins in the establishment of transgenerational response, we used dcl2, dcl3 and dcl4 mutants in parallel with wild-type plants. These studies revealed that leaf number decreased in the progeny of UV-C stressed plants, and bolting occurred later. Transposons were also re-activated in the progeny of stressed plants. Changes in the dcl mutants were less prominent than in wild-type plants. DCL2 and DCL3 appeared to be more important in the transgenerational stress memory than DCL4 because transgenerational changes were less profound in the dcl2 and dcl3 mutants.
    Plant signaling & behavior 11/2014;
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    ABSTRACT: Abstract We recently showed that a Rab protein, CPRabA5e (CP = chloroplast localized), is located in chloroplasts of Arabidopsis thaliana where it is involved in various processes, such as thylakoid biogenesis and vesicle transport. Using a yeast two-hybrid method, CPRabA5e was shown to interact with a number of chloroplast proteins, including the CURVATURE THYLAKOID 1A (CURT1A) protein and the light-harvesting chlorophyll a/b binding protein (LHCB1.5). CURT1A has recently been shown to modify thylakoid architecture by inducing membrane curvature in grana, whereas LHCB1.5 is a protein of PSII (Photosystem II) facilitating light capture. LHCB1.5 is imported to chloroplasts and transported to thylakoid membranes using the Signal Recognition Particle (SRP) pathway. With this information as starting point, we here discuss their subsequent protein-protein interactions, given by the literature and Interactome 3D. CURT1A itself and several of the proteins interacting with CURT1A and LHCB1.5 have relations to vesicle transport and thylakoid morphology, which are also characteristics of cprabA5e mutants. This highlights the previous hypothesis of an alternative thylakoid targeting pathway for LHC proteins using vesicles, in addition to the SRP pathway.
    Plant signaling & behavior 11/2014;
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    ABSTRACT: Abstract This review focuses on the energy metabolism during pollen maturation and tube growth and updates current knowledge. Pollen tube growth is essential for male reproductive success and extremely fast. Therefore, pollen development and tube growth are high energy-demanding processes. During the last years, various publications (including research papers and reviews) emphasize the importance of mitochondrial respiration and fermentation during male gametogenesis and pollen tube elongation. These pathways obviously contribute to satisfy the high energy demand, and there are many studies which suggest that respiration and fermentation are the only pathways to generate the needed energy. Here, we review data which show for the first time that in addition plastidial glycolysis and the balancing of the ATP/NAD(P)H ratio (by malate valves and NAD(+) biosynthesis) contribute to satisfy the energy demand during pollen development. Although the importance of energy generation by plastids was discounted during the last years (possibly due to the controversial opinion about their existence in pollen grains and pollen tubes), the available data underline their prime role during pollen maturation and tube growth.
    Plant signaling & behavior 11/2014;
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    ABSTRACT: Abstract Enhancement of callus induction and its regeneration efficiency through in vitro techniques has been optimized for two abiotic stresses (salt and air desiccation) using three rice genotypes viz. BR10, BRRI dhan32 and BRRI dhan47. The highest frequency of callus induction was obtained for BRRI dhan32 (64.44%) in MS medium supplemented with 2, 4-D (2.5 mgL(-1)) and Kin (1.0 mgL(-1)). Different concentrations of NaCl (2.9, 5.9, 8.8 and 11.7 gL(-1)) were used and its effect was recorded on the basis of viability of calli (VC), relative growth rate (RGR), tolerance index (TI) and relative water content (RWC). It was observed that in all cases BRRI dhan47 showed highest performance on tolerance to VC (45.33%), RGR (1.03%), TI (0.20%) and RWC (10.23%) with 11.7 gL(-1) NaCl. Plant regeneration capability was recorded after partial air desiccation pretreatment to calli for 15, 30, 45 and 60 h. In this case BRRI dhan32 gave maximum number of regeneration (76.19%) when four weeks old calli were desiccated for 45 h. It was observed that air desiccation was 2-3 folds more effective for enhancing green plantlet regeneration compared to controls. Furthermore, desiccated calli also showed the better capability to survive in NaCl induced abiotic stress; and gave 1.9 fold (88.80%) increased regeneration in 11.7 gL(-1) salt level for BRRI dhan47. Analysis of variance (ANOVA) showed that the genotypes, air desiccation and NaCl had significant effect on plant regeneration at P < 0.01.
    Plant signaling & behavior 11/2014;
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    ABSTRACT: Abstract Successful execution of germination program greatly depends on the seeds' oxidative homeostasis. We recently identified new roles for the H2O2-reducing enzyme ascorbate peroxidase 6 (APX6) in germination control and seeds' stress tolerance. APX6 replaces APX1 as the dominant APX in dry seeds, and its loss-of-function results in reduced germination due to over accumulation of ROS and oxidative damage. Metabolic analyses in dry apx6 seeds, revealed altered homeostasis of primary metabolites including accumulation of TCA cycle metabolites, ABA and auxin, supporting a novel role for APX6 in regulating cellular metabolism. Increased sensitivity of apx6 mutants to ABA or IAA in germination assays indicated impaired perception of these signals. Relative suppression of ABI3 and ABI5 expression, and induction of ABI4, suggested the activation of a signaling route inhibiting germination in apx6 seeds that is independent of ABI3. Here we provide additional evidence linking ABI4 with ABA- and auxin-controlled inhibition of germination and suggest a hypothetical model for the role of APX6 in the regulation of the crosstalk between these hormones and ROS.
    Plant signaling & behavior 11/2014;
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    ABSTRACT: ABSTRACT The fourth basic circuit element, a memristor, is a resistor with memory that was postulated by Chua in 1971. Here we found that memristors exist in vivo. The electrostimulation of the Mimosa pudica by bipolar sinusoidal or triangle periodic waves induce electrical responses with fingerprints of memristors. Uncouplers carbonylcyanide-3-chlorophenylhydrazone and carbonylcyanide-4-trifluoromethoxy-phenyl hydrazone decrease the amplitude of electrical responses at low and high frequencies of bipolar sinusoidal or triangle periodic electrostimulating waves. Memristive behavior of an electrical network in the Mimosa pudica is linked to the properties of voltage gated ion channels: the channel blocker TEACl reduces the electric response to a conventional resistor. Our results demonstrate that a voltage gated K(+) channel in the excitable tissue of plants has properties of a memristor. The discovery of memristors in plants creates a new direction in the modeling and understanding of electrical phenomena in plants.
    Plant signaling & behavior 10/2014;
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    ABSTRACT: Abstract ETHYLMALONIC ENCEPHALOPATHY PROTEIN1 (ETHE1), encoding sulfur dioxygenase activity is believed to be an important candidate in sulfur metabolism, where it is involved in amino acid catabolism during carbohydrate starvation and embryo development as seen in Arabidopsis thaliana. OsETHE1, an ETHE1-encoding gene from rice, is in fact induced in response to abiotic stresses, condition which affects nutritional status of the plant, reflecting the need for nutrient remobilization. Sulfur reduction and assimilation are believed to be light-dependent processes and so the genes involved in sulfur oxidation must also be investigated for light-dependent regulatory effects. To this end, we show that the stress response of OsETHE1 is dependent on light and that darkness largely suppresses the stress response of this gene. However, the observed regulatory effect is intricate, varying according to the stress imposed; thereby suggesting the involvement of various aspects of signaling in this process.
    Plant signaling & behavior 10/2014;
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    ABSTRACT: Abstract Transport of proteins via the secretory pathway is controlled by a combination of signal dependent cargo selection as well as unspecific bulk flow of membranes and aqueous lumen. Using the plant vacuolar sorting receptor as model for membrane spanning proteins, we have distinguished bulk flow from signal mediated protein targeting in biosynthetic and endocytic transport routes and investigated the influence of transmembrane domain length. More specifically, long transmembrane domains seem to prevent ER retention, either by stimulating export or preventing recycling from post ER compartments. Long transmembrane domains also seem to prevent endocytic bulk flow from the plasma membrane, but the presence of specific endocytosis signals overrules this in a dominant manner.
    Plant signaling & behavior 10/2014;
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    ABSTRACT: Recognition of pathogen-associated molecular patterns (PAMPs) such as flagellin, a main component of the bacterial flagellum, constitutes the first layer of plant immunity and is referred to as PAMP-triggered immunity (PTI). The rice avirulent N1141 strain of gram-negative phytopathogenic bacterium, Acidovorax avenae, induces PTI including H2O2 generation, while flagellin from the rice virulent K1 strain of A. avenae does not induce these immune responses. Mass spectrometry analyses revealed that total 1,600-Da and 2,150-Da of glycan residues were present on the flagellins from N1141 and K1, respectively. A deglycosylated K1 flagellin induced immune responses in the same manner as N1141 flagellin, suggesting that the glycan in K1 flagellin prevent epitope recognition in rice. We identified three genes in K1 flagella operon, which regulate structural modification of glycan in K1 flagellin. The immature glycan-attached flagellin from three genes deletion mutant, KΔ3FG, induced H2O2 generation in cultured rice cells, whereas the K1 mature-type flagellin did not cause a detectable increase in H2O2. The data indicate that the immature glycan of flagellin from KΔ3FG cannot prevent the epitope recognition in rice.
    Plant signaling & behavior 10/2014;
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    ABSTRACT: Abstract High light acclimation implicates mechanisms on various molecular levels and time scales. The recently identified small transcription factor network of APETALA 2/ETHYLENE RESPONSE FACTOR (AP2/ERF) transcription factors is triggered upon transfer of Arabidopsis to high light and depends on metabolite export and mitogen activated protein kinase activation. An experimental design was developed consisting of a low light to high light and back to low light illumination. This allowed the determination of the time point of no return post high light transfer which activates transcription of the AP2/ERF network. Within 10 seconds of high light treatment transcript levels of ERF6, ERF104, ERF105 and RRTF were triggered to increase from low to high levels within the next 10 minutes witnessing an ultrafast retrograde pathway with a very early time point of no return. This response differed profoundly from other high light-responsive transcripts such as stromal ascorbate peroxidase (sAPX) which accumulated in a dose-dependent manner or COR47.
    Plant signaling & behavior 10/2014;
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    ABSTRACT: Abstract Mitogen-activated protein (MAP) kinase cascades play important roles in plant immunity. Upon pathogen associated molecular pattern (PAMP) treatment, MPK3, MPK6 and MPK4 are quickly activated by upstream MKKs through phosphorylation. Western blot analysis using α-phospho-p44/42-ERK antibody suggests that additional MPKs with similar size as MPK4 are also activated upon PAMP perception. To identify these MAP kinases, seven candidate MPKs with similar sizes as MPK4 were selected for further analysis. Transgenic plants expressing these MPKs with a ZZ-3xFLAG double tag of 17 kD were generated and analyzed by western blot. MPK1, MPK11 and MPK13 were found to be phosphorylated upon treatment with flg22. Our study revealed additional MAPKs being activated during PAMP-triggered immunity.
    Plant signaling & behavior 10/2014;
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    ABSTRACT: Abstract Auxin, as a vital plant hormone, regulates almost every aspect of plant growth and development. We previously identified a dominant mutant, adp1-D, displaying loss of apical dominance. We also demonstrated that down-regulation of local auxin biosynthesis in adp1-D was responsible for the bushy phenotype of this mutant. Consistent with the reduction of local auxin biosynthesis, we recently discovered that protein abundance of PIN1, PIN3, and PIN7 was reduced in adp1-D without accompanying transcription level changes. Additionally, subcellular analysis revealed that over-expression of ADP1 inhibited endocytosis of PIN proteins. Taken together, we conclude that ADP1 regulates plant architecture through the fine-tuning of local auxin biosynthesis and through post-transcriptional regulation of auxin transporters.
    Plant signaling & behavior 10/2014;
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    ABSTRACT: Abstract Using a cuvette for simultaneous measurement of net photosynthesis in above ground plant organs and root respiration we investigated the effect of reduced leaf glucokinase activity on plant carbon balance. The gin2-1 mutant of Arabidopsis thaliana is characterized by a 50 % reduction of glucokinase activity in the shoot, while activity in roots is about fivefold higher and similar to wild type plants. High levels of sucrose accumulating in leaves during the light period correlated with elevated root respiration in gin2-1. Despite substantial respiratory losses in roots, growth retardation was moderate, probably because photosynthetic carbon fixation was simultaneously elevated in gin2-1. Our data indicate that futile cycling of sucrose in shoots exerts a reduction on net CO2 gain, but this is over-compensated by the prevention of exaggerated root respiration resulting from high sucrose concentration in leaf tissue.
    Plant signaling & behavior 10/2014;